The invention pertains to a cleaning apparatus for cleaning a running dirty surface in a machine in the graphics industry and particularly to a pneumatic pressure apparatus for moving a cleaning cloth to and away from the surface, e.g., of a cylinder.
A cleaning apparatus of this type is disclosed by U.S. Pat. No. 4,344,361 (DE 30 05 469 C2). On its path from a clean cloth roller to a pressing element in the form of an inflatable rubber lip, a cleaning cloth is moistened by a nozzle apparatus. After the rubber lip, the cloth is wound up onto a dirty cloth roller. The onward transport or advance of the cleaning cloth is carried out in each case only when the cleaning cloth is not pressed by the rubber lip against the surface to be cleaned, but is moved out of contact with that surface and, as a result, is at a short distance from it.
Further prior art concerning such apparatus includes DE 196 05 957 A1, DE 195 16 422 C2, DE 41 42 422 A1, DE 30 05 469 C2, U.S. Pat. Nos. 5,842,418, 5,699,738.
Dirty surfaces in machines in the graphics industry, in printing machines, include the various cylinders, such as the blanket cylinders, printing-plate cylinders and impression cylinders, and also paper webs and paper sheets to be printed. In paper cutting machines (slitters or sheet cutters) and in paper coating equipment, further dirty surfaces are the paper webs or paper sheets, and particularly also cylinders and rollers which are used to transport and to treat the paper webs and paper sheets. xe2x80x9cDirtxe2x80x9d is, in particular, printing ink and paper dust, but includes any other contamination.
During a cleaning operation, the machine being cleaned continues to run, but without paper sheets or paper webs being able to be printed, if printing ink and other types of contamination are being removed from one of the cylinders, such as a printing-plate cylinder, blanket cylinder or impression cylinder. This means that paper broke (rejects) is produced by the paper running during the cleaning operation. During the cleaning operation, the cleaning cloth is pressed cyclically many times, either by the rubber lip or by another pressing element, against the surface to be cleaned and the cloth is then lifted off the surface again. The cleaning cloth is transported onward by a predetermined cloth section in each case when it is lifted off, in order that when the cloth is again placed against the surface to be cleaned, a fresh cloth section is available.
The invention is intended to achieve the object of shortening, in a straightforward way, the time required for a cleaning operation.
The invention concerns a cleaning apparatus for a surface and particularly for a surface in the graphics industry and more particularly for the surface of a cylinder in the graphics industry. A pressing element has a cleaning cloth thereover and the pressing element is movable toward and away from the surface. A pressurizable pressure chamber which when pressurized, acts on the pressing element to move the cloth to the surface. A pneumatic circuit feeds compressed air to the pressure chamber and vents the pressure chamber. The circuit includes a compressed air storage chamber which can be alternatively connected to the pressure chamber or the pressure element to pressurize the pressure chamber or connected to a compressed air source to refill the chamber with compressed air. The volume of the chamber and the pressure therein is higher than that of the pressure needed in the pressure chamber for rapid refilling of the pressure chamber. A second air path communicates between the compressed air source and the pressure chamber and includes valving enabling venting of the pressure chamber to maintain a selected pressure level.
The invention provides a cleaning apparatus for cleaning a running dirty surface, wherein the pneumatic circuit contains a compressed-air store with a compressed-air storage chamber, which can be connected alternatively to the pressure chamber of the pressing element, in order to press the pressing element into the in-contact position by means of stored compressed air, or to a compressed-air source, in order to fill that chamber with compressed air again. The volume of the compressed-air storage chamber is less than the volume of the pressure chamber, and the compressed air stored in the compressed-air storage chamber is at a significantly higher pressure than a predetermined desired pressure value to be produced in the pressure chamber in the in-contact position of the pressing element, for the cleaning operation. This causes a high flow velocity of the compressed air from the compressed-air storage chamber into the pressure chamber is achieved.
According to a preferred embodiment of the invention, the compressed-air store has a piston which can be actuated pneumatically to force the stored quantity of compressed air from the compressed-air storage chamber into the pressure chamber of the pressing element.
Furthermore, the invention provides a compressed-air feed line from the compressed-air source to the compressed-air storage chamber which is provided with a pressure regulator which sets the pressure in the compressed-air storage chamber to a value which is significantly higher than the pressure with which the pressing element is to be held in the in-contact position. The pressure value and the volume of the compressed-air storage chamber are selected such that the stored quantity of compressed air is at least as great as the quantity of compressed air which is needed in the pressure chamber to produce the pressure with which the pressing element is to be held in the in-contact position.
In a particularly preferred embodiment of the invention, the compressed-air storage chamber is arranged in a first compressed-air path, which leads from the compressed-air source to the pressure chamber of the pressing element. A second compressed-air path leads from the compressed-air source to the pressure chamber of the pressing element. The second compressed-air path is provided with a pressure regulator which is set to the pressure with which the pressing element is to be held in the in-contact position.
In a further preferred embodiment of the invention, at its downstream end, each of the two compressed-air paths can alternatively be connected to the pressure chamber of the pressing element or isolated from this pressure chamber by a valve arrangement.
The invention is suitable in particular for cleaning printing-machine cylinders and, in particular, also for cleaning impression cylinders in sheet-fed printing machines.
Other objects and features of the invention are described below with reference to the attached drawings and using a preferred embodiment as an example.